Research On Attribute-based Signature Technologies For Cloud Storage Security

With the continuous development of cloud computing technology,more and more individuals and enterprises choose to use cloud storage applications to store data.As an emerging application mode,cloud storage provides users with services such as fast data storage and retrieval,which effectively solves the data storage problems caused by the explosive growth of data.However,the user loses the control of the data stored in the cloud,and the cloud storage server is not completely reliable,the security problems such as users' private data leakage and data tampering occur frequently in the cloud storage,which seriously hinders the further development and application of cloud storage.Attribute-based Signature(ABS),as an important branch of digital signature,not only guarantees the integrity of cloud stored data,but also provides fine-grained access control over data,which has important application value in industrial Internet of Things and mobile medical scenarios.Aiming at the efficiency and security problems of the existing ABS schemes,two secure and efficient ABS schemes are proposed in this thesis.The main contributions are as follows:The existing server-aided ABS schemes can reduce the computing overhead of signer and verifier simultaneously by using server-aided technologies.However,these schemes lack the detection mechanism of outsourcing signature,and there may be collusion attacks from the signer and cloud server.To solve these problems,a server-aided and verifiable ABS scheme is proposed.In this scheme,the user first verifies the validity of the partial signature generated by the cloud server when signing,and then continues to generate the complete signature if the verification is passed.Otherwise,the signature is terminated,which ensures the security of the outsourcing signature.In the signature verification phase,the bilinear pairing operation involving the message is performed by the verifier,thus the collusion attack from the signer and cloud server is effectively resisted.The security proofs and simulation analysis show that the scheme can ensure the efficiency while improving the security.Since the traditional ABS schemes only support small universe,and the size of attribute set space needs to be preset in the system initialization phase,which makes the system operation become complicated.In addition,the existing ABS schemes supporting large universe have a large amount of computing overhead in the signature phase.To solve these problems,an ABS scheme supporting large universe and computing outsourcing is proposed.Firstly,the scheme supports large universe and avoids the shortcoming of presetting the size of attribute space.Secondly,the scheme outsources a lot of computation in the signing process,and provides a detection mechanism for outsourcing signature,so as to avoid forgery of partial signature by the cloud server.In addition,the scheme adopts the on-chain off-chain storage mode by combining blockchains and the cloud server to store ciphertext data,which greatly facilitates the secure storage and sharing of ciphertext data.The security analysis and experimental results show that the proposed scheme improves the efficiency of the system while ensuring the security of the outsourcing signature.